Methods and systems for generating a mission plan that guides a spacecraft to orbiting target objects

Abstract

An example method executed by a controller onboard a spacecraft generates a mission plan in real-time that guides the spacecraft along a space autonomous mission to rendezvous with two or more orbiting target objects. The method includes establishing potential permutations for all possible unique maneuver sequences in which to visit the two or more orbiting target objects, and for each potential permutation, determining a collision-free maneuver plan for defining orbit trajectories to intercept each of the two or more orbiting target objects for each of the possible unique maneuver sequences. An optimal permutation is determined that meets viewing constraints of the two or more orbiting target objects, a viewing priority, and fuel constraints of the spacecraft. A mission visit plan is generated using the optimal permutation, and the spacecraft executes the plan to rendezvous with and inspect the two or more orbiting target objects.

What is claimed is: 
     
       1. A method executed by a controller onboard a spacecraft to generate a mission plan in real-time that guides the spacecraft along a space autonomous mission to rendezvous with two or more orbiting target objects, the method comprising:
 establishing, for two or more orbiting target objects to visit, potential permutations for all possible unique maneuver sequences in which to visit the two or more orbiting target objects; 
 for each potential permutation, determining a collision-free maneuver plan for defining orbit trajectories to intercept each of the two or more orbiting target objects for each of the possible unique maneuver sequences; 
 based on the collision-free maneuver plan for each potential permutation, determining an optimal permutation from the potential permutations that meets viewing constraints of the two or more orbiting target objects, a viewing priority, and fuel constraints of the spacecraft, wherein the optimal permutation is further based on an orbit transfer location of the spacecraft and an inspection starting location on the two or more orbiting target objects; 
 generating a mission visit plan, using the optimal permutation, for the spacecraft to rendezvous with and inspect the two or more orbiting target objects; and 
 causing the spacecraft to rendezvous with and inspect the two or more orbiting target objects according to the mission visit plan. 
 
     
     
       2. The method of  claim 1 , wherein establishing potential permutations for all possible unique maneuver sequences in which to visit the two or more orbiting target objects comprises:
 utilizing a pathfinding algorithm for gaming for determining all potential permutations for all possible unique maneuver sequences in which to visit the two or more orbiting target objects. 
 
     
     
       3. The method of  claim 2 , wherein the pathfinding algorithm for gaming is an A* algorithm. 
     
     
       4. The method of  claim 1 , wherein determining the collision-free maneuver plan for each of the possible unique maneuver sequences comprises:
 calculating a transfer orbit relative intercept location based on current expected spacecraft and target object positions, velocities, and orbital parameters. 
 
     
     
       5. The method of  claim 1 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on intercept success of the two or more orbiting targets, the viewing priority, and remaining fuel of the spacecraft; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that has no rendezvous intercept failures and has a highest fuel remaining on the spacecraft. 
 
     
     
       6. The method of  claim 1 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on solar point constraints or sun exclusion zones; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that meets the solar point constraints and has a highest fuel remaining on the spacecraft. 
 
     
     
       7. The method of  claim 1 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on orbit trajectory limitations due to a point of closest approach; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that meets the orbit trajectory limitations and has a highest fuel remaining on the spacecraft. 
 
     
     
       8. The method of  claim 1 , further comprising:
 after causing the spacecraft to begin the mission visit plan, receiving an update to at least one of a location of the two or more orbiting target objects and a spacecraft collision possibility; 
 based on the update to the at least one of the location of the two or more orbiting target objects and the spacecraft collision possibility, reevaluating an ability to execute the mission visit plan according to specified mission maneuvers, number and type of target observations, and available time to accomplish target encounters; and 
 based on constraints of meeting the specified mission maneuvers, updating the mission visit plan to modify an inspection time per target. 
 
     
     
       9. The method of  claim 1 , further comprising:
 after causing the spacecraft to begin the mission visit plan, updating position and velocity status on each of the two or more orbiting target objects and checking for a possible collision event with the spacecraft; and 
 based on updates to the position and velocity on each of the two or more orbiting target objects, updating the mission visit plan by performing one or more of modifying an orbit transfer time of the spacecraft, modifying wait times to rendezvous or perform inspection, or modifying a maneuver trajectory of the spacecraft. 
 
     
     
       10. The method of  claim 1 , wherein for each of the two or more orbiting target objects, multiple inspection points exist, and the method further comprises:
 establishing the potential permutations for all possible unique sequences in which to visit the two or more orbiting target objects to include permutations for at least two or more inspection points on each target object. 
 
     
     
       11. A method executed by a controller onboard a spacecraft to generate a mission plan in real-time that guides the spacecraft along a space autonomous mission to rendezvous with at least one orbiting target object, the method comprising:
 establishing, for at least one orbiting target object to be inspected at two or more inspection points, potential permutations for all possible unique maneuver sequences in which to visit the at least one orbiting target object and perform inspections at the two or more inspection points; 
 for each potential permutation, determining a collision-free maneuver plan for defining orbit trajectories to intercept the at least one orbiting target object and perform inspections at the two or more inspection points for each of the possible unique maneuver sequences; 
 based on the collision-free maneuver plan for each potential permutation, determining an optimal permutation from the potential permutations that meets viewing constraints of the two or more inspection points, a viewing priority, and fuel constraints of the spacecraft, wherein the optimal permutation is further based on an orbit transfer location of the spacecraft and an inspection starting location of the at least one orbiting target object; 
 generating a mission visit plan, using the optimal permutation, for the spacecraft to rendezvous with the at least one orbiting target object and perform inspections at the two or more inspection points; and 
 causing the spacecraft to rendezvous with the at least one orbiting target object and perform inspections at the two or more inspection points according to the mission visit plan. 
 
     
     
       12. The method of  claim 11 , wherein:
 the at least one orbiting target object has the two or more inspection points, each of which requires a different orbital approach trajectory by the spacecraft for visiting; and 
 the different orbital approach trajectory depends on an order in which the two or more inspection points are visited. 
 
     
     
       13. The method of  claim 11 , wherein determining the collision-free maneuver plan for each of the possible unique maneuver sequences comprises:
 based on a unique maneuver sequence within a potential permutation that violates the viewing constraints of the two or more inspection points, the viewing priority, or the fuel constraints of the spacecraft, backtracking to a previous inspection point in the unique maneuver sequence as a next inspection point in the unique maneuver sequence to consider. 
 
     
     
       14. The method of  claim 11 , wherein determining the collision-free maneuver plan for each of the possible unique maneuver sequences comprises:
 based on a specific inspection point in a unique maneuver sequence not being viable, removing all subsequent permutations from further consideration. 
 
     
     
       15. The method of  claim 11 , wherein determining the collision-free maneuver plan for each of the possible unique maneuver sequences comprises:
 calculating a transfer orbit relative intercept location based on current expected spacecraft and target object positions, velocities, and orbital parameters. 
 
     
     
       16. The method of  claim 11 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on intercept success of the two or more inspection points, the viewing priority, and remaining fuel of the spacecraft; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that has no rendezvous intercept failures and has a highest fuel remaining on the spacecraft. 
 
     
     
       17. The method of  claim 11 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on solar point constraints or sun exclusion zones; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that meets the solar point constraints and has a highest fuel remaining on the spacecraft. 
 
     
     
       18. The method of  claim 11 , wherein determining the optimal permutation from the potential permutations comprises:
 ranking each potential permutation based on orbit trajectory limitations due to a point of closest approach; and 
 selecting the optimal permutation from the potential permutations to be a potential permutation that meets the orbit trajectory limitations and has a highest fuel remaining on the spacecraft. 
 
     
     
       19. The method of  claim 11 , further comprising:
 after causing the spacecraft to begin the mission visit plan, receiving an update to at least one of a location of the at least one orbiting target object and a spacecraft collision possibility; 
 based on the update to the at least one of the location of the at least one orbiting target object and the spacecraft collision possibility, reevaluating an ability to execute the mission visit plan according to specified mission maneuvers, number and type of target observations, and available time to accomplish target encounters; and 
 based on constraints of meeting the specified mission maneuvers, updating the mission visit plan to modify an inspection time per target. 
 
     
     
       20. An onboard mission controller for a spacecraft, comprising:
 a processor; and 
 non-transitory computer-readable media having stored therein instructions, which when executed by the processor, cause the spacecraft to perform functions comprising:
 establishing, for two or more orbiting target objects to visit, potential permutations for all possible unique maneuver sequences in which to visit the two or more orbiting target objects; 
 for each potential permutation, determining a collision-free maneuver plan for defining orbit trajectories to intercept each of the two or more orbiting target objects for each of the possible unique maneuver sequences; 
 based on the collision-free maneuver plan for each potential permutation, determining an optimal permutation from the potential permutations that meets viewing constraints of the two or more orbiting target objects, a viewing priority, and fuel constraints of the spacecraft, wherein the optimal permutation is further based on an orbit transfer location of the spacecraft and an inspection starting location on the two or more orbiting target objects; 
 generating a mission visit plan, using the optimal permutation, for the spacecraft to rendezvous with and inspect the two or more orbiting target objects; and 
 causing the spacecraft to rendezvous with and inspect the two or more orbiting target objects according to the mission visit plan.